Thats all most folks want. To say that, leads me to believe you dont understand what goes into making one. They take a long time to fabricate, and can be quite expensive to mold, make a first cast, tweak the fine details, and remold. Noone wants to make a crappy rough piece, they want to create a nice clean cast, we are artists essentially, so that all takes time, and is factored into the final cost. They are also a large complicated piece to cast with many parts that go to it. It takes alot of supplies (which arent cheap) and takes alot of time to cast one, hence the cost and wait. Unfortunately there is no button to push that pops out a jetpack..not yet anyway lol.
All that said, As far as i know MOW makes the least expensive pack. at i believe $350, free shipping. They are slush cast resin and a little heavier than the fiberglass ones, but it is still a very nice pack and one of the most common currently. He usually has stock so you get it pretty fast. Mine are $325 plus shipping so it may be around the same or a little more price wise depending where its going. I make them in runs. I take a certain amount of orders then stop, fill those all, then i will take more if folks want them at that time. Mine are fiberglass. Fettseven and NME are the same pack, (fettseven made the pack NME sells) not sure of their pricing or wait times though. Theirs is also fiberglass. FP is likely the most accurate, and one of the more pricey ones, but your getting a more accurate pack and his craftmanship is the best ive seen, so your paying for those advantages. His is also fiberglass. You'd have to contact the makers for exact pricing and wait times though, as the wait for Jetpacks tend to be long mostly because of how much work goes into casting one.